1. Field of the Invention
This invention relates to a highly active titanium trichloride catalytic component advantageously usable for the manufacture of an .alpha.-olefin which has a high degree of stereospecificity. The invention also relates to a method for carrying out homo- or co-polymerization of an .alpha.-olefin by which a highly crystalline polymer can be manufactured in the presence of the above stated titanium trichloride catalytic component and an organo-aluminum compound.
More particularly stated, the invention relates to a titanium trichloride catalytic component which is obtained in the following manner: In having the titanium trichloride catalytic component separated out of a solution prepared by dissolving titanium tetrachloride, an organic ether compound and an organo-aluminum compound in a solvent, a mixture solvent consisting of a saturated aliphatic hydrocarbon and/or an alicyclic hydrocarbon with concomitance therein of at least 3% by volume and not exceeding 20% by volume of an aromatic hydrocarbon halide is employed as the solvent either in the presence or absence of an olefin; the organo-aluminum compound, the titanium tetrachloride and the organic ether compound are added at a solvent temperature not exceeding 55.degree. C.; after that the solvent temperature is raised up to 45.degree.-150.degree. C. over a period of 10 minutes to 24 hours; when temporary cooling is performed during the temperature raising process or when the solvent temperature of 45.degree.-80.degree. C. is reached during the temperature raising process, the organic ether compound and/or titanium tetrachloride is further added during the cooling process or at the solvent temperature of 45.degree.-80.degree. C., and, through these processes, a titanium trichloride catalytic component having an average particle diameter between 10 and 500.mu. is separated from the solution. The invention further relates, as mentioned in the foregoing, to the method for homo- or co-polymerization of an .alpha.-olefin in the presence of a catalyst system consisting of the above stated titanium trichloride and an organo-aluminium compound.
2. Description of the Prior Art
A catalytic component for .alpha.-olefin polymerization is nowadays required to satisfy the following conditions: It must have a sufficiently high polymerizing property to permit omission of deashing and washing processes for removal of the residue of the catalyst and a non-stereospecific polymer portion from a polymer produced; a high degree of productivity for a stereospecific polymer; and the catalytic component and the polymer product obtained therefrom must have suitable and uniform particle sizes. This is because a catalytic component and a polymer product that are in a powdery state having uneven particle sizes such as those obtained by the conventional method cause difficulty in separating, drying and transporting them. Such products give trouble in industrial operations and result in lower productivity.
It is further desired that the catalytic component is capable of permitting omission of a pelletizing process during the manufacture of an .alpha.-olefin polymer.
Heretofore, the operation of .alpha.-olefin polymer manufacturing plants using titanium trichloride catalytic components which are obtained through the conventional method has included processes of drying a powdery polymer which is obtained through a polymerization process; melting, milling, extruding and shaping to pelletize the polymer; and supplying the polymer product thus obtained to a molding field. At such an .alpha.-olefin polymer manufacturing plant, the pelletizing processes require the largest portion of the total cost of facilities and consume a very large amount of energy. Therefore, in a polymerizing process, if the conventional catalytic component could be replaced with a catalytic component which permits the manufacture of a polymer having highly uniform particle diameter without including any fine particles thereof, it would be possible not only to enhance the operation efficiency of the polymer manufacturing plant but also to obviate the necessity of carrying out the processes of pelletizing the polymer produced. This would save an enormous amount of expenses of facilities and energy and would greatly contribute to the rationalization of the polymer manufacturing operation. Therefore, development of such an ideal catalytic component has been longed for.
Heretofore, a Ziegler-Natta catalyst has been used in general for polymerization of an .alpha.-olefin. A typical example of this is a catalyst system obtained by a combination of a .delta.-type titanium trichloride-aluminum chloride eutectic mixture (hereinafter will be referred to as the .delta.-type eutectic mixture) with an organo-aluminum compound. The .delta.-type eutectic mixture is obtained in the following manner: A .gamma.-type titanium trichloride-aluminum chloride eutectic mixture (hereinafter will be referred to as the .gamma.-type eutectic mixture), which is obtained by reducing titanium tetrachloride with aluminum powder in the presence of aluminum chloride, is activated by pulverizing it with a ball mill, a vibration mill or the like. With the .delta.-type eutectic mixture used as a catalytic component for polymerizing an .alpha.-olefin, however, the polymerizing activity and the productivity for a stereospecific polymer are low. Therefore, the .delta.-type eutectic mixture is not satisfactory. Hence, there have been proposed many reforming methods for improving the .delta.-type eutectic mixture. Such proposed methods include, for example: (1) A method of pulverizing the .gamma.-type eutectic mixture or the .delta.-type eutectic mixture together with an improving agent such as an electron donor compound or the like or by allowing the former to react with the latter; (2) a method of washing the .gamma.-type or .delta.-type eutectic mixture or the pulverized matter of the above stated method (1) with an inert hydrocarbon solvent; and (3) a method of heat treating the .gamma.-type or .delta.-type eutectic mixture or the matter of the above stated method (1) or (2).
Improvement in the polymerizing activity of the catalytic component and the productivity thereof for a stereospecific polymer has been possible to a certain extent by these methods. However, these methods not only have been entirely unable to freely control the particle diameter of the catalytic component but also have been far from attaining the aim of obviating the necessity of the deashing and washing processes on the polymer produced.
Recently, some catalytic components that have high polymerizing activity and also a high productivity for a stereospecific polymer have been developed. Such recent development include, for example, a method disclosed by a Japanese patent application laid-open No. 47-34478 in which: (1) Titanium tetrachloride is reduced with an organo-aluminum at a low temperature to obtain a .beta.-type titanium trichloride-aluminum chloride eutectic mixture (hereinafter will be referred to as the .beta.-type eutectic mixture); (2) then, a part of the aluminum compound contained in the .beta.-type eutectic mixture is removed by treating the .beta.-type eutectic mixture with a complexing agent; and (3), following that, the .beta.-type eutectic mixture is heat treated in titanium tetrachloride to obtain a .delta.-type eutectic mixture presenting a dark purple color. Compared with the catalytic component of the .delta.-type eutectic mixture which is obtained by the above stated pulverization process, the catalytic component obtained by this manufacturing method has polymerizing activity several times as great as that of the former and is an excellent catalytic component. However, this catalytic component has the following shortcomings: (1) A long period of time is required for the manufacture of this catalytic component; (2) a great amount of a washing liquid is required for washing it; (3) there will be produced a great amount of a waste liquid containing titanium and aluminum ions; and (4) accordingly, it necessitates the use of a great amount of a neutralizing agent and, therefore, necessitates some environmental pollution preventing measures and the use of an enormous amount of energy for recovering the solvent used. Therefore, the cost of manufacturing this catalytic component becomes extremely high.
To eliminate the above stated shortcomings, there have been also proposed various methods for manufacturing a catalytic component including: (1) A method in which titanium tetrachloride is treated with an organo-aluminum compound expressed by a generic formula AlRnX.sub.3 -n (wherein R represents an alkyl group of carbon number 1-10, X a halogen atom and n a real number of 0&lt;n.ltoreq.3) in the presence of an organic ether compound to obtain a liquid matter; and then the liquid matter is brought into contact with a liberating agent such as Lewis acid or the like at a temperature not exceeding 150.degree. C. to separate therefrom a fine powdery titanium trichloride catalytic component (Japanese patent appln. laid-open No. 51-16298 and 51-76196). (2) A method which is an improvement over the above stated method (1) and does not use the liberating agent (Japanese patent appln. laid-open No. 52-47594). (3) A method which is similar to the above stated method (1) except that a titanium trichloride catalytic component is separated by using a seed crystal (Japanese patent appln. laid-open No. 51-94496). (4) A method similar to the above stated method (1) except that a titanium trichloride catalytic component is separated with the operation temperature changed (Japanese patent appln. laid-open No. 51-90998). These catalytic component manufacturing methods do not require the use of a solvent in great quantity and produce not much waste liquids. However, the average particle diameter of the titanium trichloride component formed is at the most about 30.mu. and is normally extremely fine measuring several .mu. or less than that. Besides, since the bulk density of the titanium trichloride catalytic component is low, it is difficult to handle the catalytic component. Further, when an .alpha.-olefin is polymerized using this catalytic component, the particle diameter and the bulk density of the polymer produced are small; the productivity for a stereospecific polymer is low; and the polymer must be pelletized because it is in a powdery state.
As mentioned in the foreoging, the .alpha.-olefin polymerizing catalytic components manufactured in accordance with the conventional and prior art methods are not satisfactory in various properties. The properties of the olefin polymers obtained through polymerization carried out in the presence of these catalytic components are also not satisfactory. Further improvement of them, therefore, has been desired.
Meanwhile, the present inventors have previously proposed methods for manufacturing titanium trichloride catalytic components as recited by unexamined Japanese patent publication Nos. 54-90094, SHO 55-3456 and SHO 56-8411. The titanium trichloride catalytic component obtained in accordance with each of these methods has a high degree of polymerizing activity and a high rate of producing a stereospecific polymer. The catalytic component also permits control over the particle diameter thereof as desired and eventually permits to control the particle diameter of the olefin polymer to be obtained by the use thereof, so that pelletizing processes can be omitted. The inventors have further conducted studies to better the titanium trichloride catalytic component which is obtainable in accordance with these previously proposed method and which has relatively large particle diameter measuring more than 100.mu.. The present invention has been completed through these further studies.